Self-monitoring of blood glucose levels requires a user to extract a discrete volume of capillary blood (typically from the fingertip) and place the extracted blood on a disposable element for analysis. The blood extraction is generally accomplished by lancing and subsequently “milking” the lanced site to express a sufficient volume of blood for analysis. After the user has produced a skin opening in a finger by lancing, the finger is “milked”, i.e., massaged or squeezed, to draw blood through the opening.
While blood volume requirements of electromechanical sensors have dropped to sub-microliter levels, users typically still need to “milk” the lanced sites to express enough blood to trigger a sensor. The “milking” process adds another step and level of complexity to the task of obtaining a blood glucose measurement.
A typical lancing device 100 is shown FIG. 1. A nose portion 104 has a surface 168 at a distal end for pressing against a patient's flesh. A lancet stylet passes through a nose orifice 184 formed in the nose portion 104 when activated by the release member 138. Indication marks of the position of the lancet stylet are visible through a window 112, which is covered by a translucent lens 115. According to one embodiment, however, the translucent lens 115 is omitted. An adjustment collar 106 is rotatable around the nose portion 104 to set the desired depth of penetration. Bumps or knurls 114 on the adjustment collar 106 facilitate rotation of the adjustment collar. A distal end 228 of a body assembly 136 is connected to the nose portion 104. A knob cap 122 is disposed at a proximal end 230 of the body assembly 136. The assembly and operation of the lancing device 100, as shown in FIG. 1, is described in commonly-owned U.S. Pat. No. 6,558,402, which issued on May 6, 2003, and is hereby incorporated by reference in its entirety.
Devices currently exist that attempt to eliminate the need to “milk” a lanced site. For example, one device, Bayer's Vaculance®, applies a vacuum after lancing to cause the skin to bulge upwardly to better express blood. Another device, Abbott's Soft-Tact™, applies a vacuum both before and after lancing to stretch the skin to better express blood. However, these vacuum devices are intended for off-finger use exclusively. Accordingly, a need exists for a lancing device that does not require the user to “milk” the lanced site to express blood and is usable on the user's fingertip.
Furthermore, vacuum application requires sufficient surface area to create a seal between the vacuum device and the user's skin. Creating a vacuum on a topographically non-uniform surface, such as a fingertip, is difficult. Typically, the user uses a flat surface as a support to successfully achieve the necessary seal. Accordingly, a need exists for a lancing device that does not require a seal around the lanced site or a flat surface to support the lancing device.